Organic light-emitting diode (OLED) display devices have the advantages of low power consumption, high color gamut, high brightness, high resolution, wide viewing angle and high response speed. The OLED display device can be divided into two categories: a passive matrix OLED (PMOLED) and an active matrix OLED (AMOLED) according to a driving mode. Wherein the AMOLED has a matrix arrangement of pixels, belonging to the active display type, high luminous efficiency, usually used for high-definition large-size display device.
AMOLED is a current-driven device. When current flows through the organic light-emitting diode, the organic light-emitting diode emits light, and the light-emitting brightness is determined by the current flowing through the organic light-emitting diode itself. Most existing integrated circuits (ICs) only transmit voltage signals, so AMOLED's pixel driving circuit needs to complete the task of converting voltage signals into current signals. The traditional AMOLED pixel drive circuit is usually 2T1C, that is, the structure of two thin film transistors plus a capacitor to convert the voltage to current.
The 2T1C pixel driving circuit traditionally used for AMOLED is sensitive to the threshold voltage and the channel mobility of the thin film transistor, the startup voltage and the quantum efficiency of the organic light-emitting diode, and the transient process of the power supply. The threshold voltage of the driving thin film transistor drifts with the working time, resulting in the unstable light emitting of the organic light-emitting diode, causing the brightness difference of the pixel driving circuit and reducing the display quality.